The present disclosure relates to an image reading apparatus for reading an image based on reflected light from a document.
Conventionally, an image forming apparatus such as a copier, facsimile machine, scanner or MFP is known which includes an image reading apparatus for reading an image based on reflected light from a contact glass. Image reading apparatuses of this type are generally roughly divided into image reading apparatuses of a reduction optical system type and image reading apparatuses of a nonmagnifcation optical system type.
An image reading apparatus of the reduction optical system type normally includes a plurality of mirrors and one optical lens and reads an image by introducing reflected light from a contact glass to the optical lens by the mirrors and imaging a reduced optical image on an image sensor functioning as a photoelectric converter. A length in a main scanning direction of the image sensor used in the image reading apparatus of the reduction optical system type is about ⅕ to 1/9 of a length in the main scanning direction of an image reading area of the contact glass.
On the other hand, an image reading apparatus of the nonmagnification optical system type normally includes a rod lens array, in which a plurality of rod lenses are arranged in an array, and reads an image by imaging reflected light from a contact glass as an unmagnified optical image on an image sensor by the rod lens array proximate to the contact glass.